Common methods for forming electrical circuit patterns on a substrate are such that after forming, on the entire surface of the substrate, a conductive film, an insulating film, a semiconductor film, and a dielectric film, employing vacuum processes such as sputtering, circuit patterning is performed employing photolithographic techniques. Photolithographic techniques, as described herein, refer to the method in which a photosensitive resist is applied onto the thin film to be subjected to patterning, and after being exposed via a photomask and developed, thin exposed film portions are subjected to dry etching or wet etching. Thereafter, commonly, the resist is peeled off and after forming a film of another material, the photolithographic process is repeated.
Recently, a method for directly forming a pattern without using a photolithographic method but using an ink-jet printing head has been tested. In this method, an ink containing a desired material for the electrical circuit is employed. By using such a method, it has become possible to simplify formation of circuit patterns.
In the above example of employing an ink-jet head, ejected ink spreads over a substrate, which prevents formation of highly resolutional patterns. Namely, it has been difficult to uniformly place an ink at a desired position on the substrate.
As a technique to overcome the problem in which the ink spreads over a substrate, for example, Japanese Patent Publication Open to Public Inspection (hereafter referred to as JP-A) No. 11-274681 discloses a technique in which an adsorbing layer for the solvent of the ink is provided on the substrate.
However, the above technique also has a problem in that the solute of the ink is not impregnated in the adsorbing layer resulting in forming an accumulation of patterning materials on the surface of the adsorbing layer, which is not suitable for manufacturing a complicated circuit pattern, for example, a three-dimensional circuit pattern.
Further, heretofore, in order to protect the accumulated ink solutes on the surface of the adsorbing layer, a protective layer has been provided. However, this method not only increases the number of work steps but also makes it difficult to use a polymer support which is suitably used for a flexible print circuit, as well as a flexible display.
Still further, WO 01/47043 discloses a technique in which by pattern formation via ejecting ink of an aqueous dispersion of conductive polymers, a source electrode and a drain electrode are formed, whereby a top gate type thin organic film transistor (an organic TFT) is prepared.
However, in this method, there have been a disadvantage that it takes time until the solution is dried and pattern formation is completed. In addition, patterning accuracy degrades due to spreading of liquid droplets. Further, since a polyimide film is employed to form a channel via photolithography, complicated process are required, resulting in further increase in the production cost.